Heart Blocks and Heart Blocks and PacemakersPacemakers

Juliette SacksJuliette Sacks

January 25, 2007January 25, 2007

Core RoundsCore Rounds

ObjectivesObjectives

► Review heart blocks, their clinical significance Review heart blocks, their clinical significance and managementand management

► Provide an overview of pacemaker components, Provide an overview of pacemaker components, nomenclature and functionsnomenclature and functions

► Discuss complications of pacemaker Discuss complications of pacemaker implantationimplantation

► Talk about pacemaker malfunctionTalk about pacemaker malfunction► Touch on ED management and disposition of Touch on ED management and disposition of

pacemaker patientspacemaker patients► Offer a precis of temporary pacing modalities.Offer a precis of temporary pacing modalities.► ICDs not covered in this talk.ICDs not covered in this talk.

CaseCase

►85 y.o. F complaining of feeling “off” 85 y.o. F complaining of feeling “off” and being “just so tired”and being “just so tired”

►Denies CP, SOBDenies CP, SOB►Vaguely recalls feeling a bit “unsteady” Vaguely recalls feeling a bit “unsteady”

on a couple of occasionson a couple of occasions►PMHx: osteoporosis, hypothyroidism PMHx: osteoporosis, hypothyroidism

and depressionand depression►Meds: Calcium, Vit D, Celexa, SynthroidMeds: Calcium, Vit D, Celexa, Synthroid

Case cont’dCase cont’d

►Vitals: Vitals: HR 45, regularHR 45, regular RR 16RR 16 BP 108/75BP 108/75 02 sats 97% on RA02 sats 97% on RA AfebrileAfebrile

Granny’s EKG:

Atrioventricular BlocksAtrioventricular Blocks

► Definition:Definition: Delay or interruption in the transmission of an Delay or interruption in the transmission of an

impulse from the atria to the ventriclesimpulse from the atria to the ventricles Conduction may be delayed, intermittent or Conduction may be delayed, intermittent or

absent.absent.► DurationDuration

TransientTransient PermanentPermanent

► Causes may be:Causes may be: AnatomicalAnatomical FunctionalFunctional

EtiologyEtiology

► Fibrosis and sclerosis of the conduction Fibrosis and sclerosis of the conduction systemsystem

► Ischemic heart diseaseIschemic heart disease► DrugsDrugs► Increased vasovagal toneIncreased vasovagal tone► Valvular diseaseValvular disease► Congenital heart diseaseCongenital heart disease► Other:Other:

Cardiomyopathies, myocarditis, hyperkalemia, Cardiomyopathies, myocarditis, hyperkalemia, infiltrating malignancies, miscellaneousinfiltrating malignancies, miscellaneous

Surgery – CABG, valve replacementSurgery – CABG, valve replacement

Sclerosis and fibrosis of the Sclerosis and fibrosis of the conduction systemconduction system

► Account for 50% of AV blockAccount for 50% of AV block► 2 idiopathic entities:2 idiopathic entities:

1.1. Lev’s Disease:Lev’s Disease:– ““sclerosis of left side of the heart”sclerosis of left side of the heart”– Affects older peopleAffects older people– Associated with calcific aortic and mitral valves that Associated with calcific aortic and mitral valves that

extends into the adjacent conduction systemextends into the adjacent conduction system

2.2. Lenegre’s Disease:Lenegre’s Disease:► Progressive fibrotic, sclerodegenerative diseaseProgressive fibrotic, sclerodegenerative disease► Affects younger peopleAffects younger people► May be hereditaryMay be hereditary► Slow progression to complete heart blockSlow progression to complete heart block► Presents with bradycardia and some degree of AVBPresents with bradycardia and some degree of AVB

Ischemic Heart DiseaseIschemic Heart Disease

► Accounts for 40% of AV blockAccounts for 40% of AV block► Chronic or acute ischemic changes can Chronic or acute ischemic changes can

disrupt conductiondisrupt conduction► With AMI:With AMI:

20% will develop AVB20% will develop AVB► 8% 18% 1stst degree AVB degree AVB► 5% 25% 2ndnd degree AVB degree AVB► 6% 36% 3rdrd degree AVB degree AVB

► Up to 20% increased mortality with Up to 20% increased mortality with bradycardia and/or blocks post AMIbradycardia and/or blocks post AMI

DrugsDrugs

► Cardiac medications: Digitalis, CCB Cardiac medications: Digitalis, CCB (especially verapamil), B-blockers(especially verapamil), B-blockers

► Class Ia: Quinidine, procainamide, Class Ia: Quinidine, procainamide, disopyramidedisopyramide

► Cholinergics: cholinesterase inhibitorsCholinergics: cholinesterase inhibitors► Opioids and sedativesOpioids and sedatives► Drugs with Class IA type effects:Drugs with Class IA type effects:

TCAs, carbamazepine, quinine, chloroquineTCAs, carbamazepine, quinine, chloroquine

► CocaineCocaine

Increased Vagal ToneIncreased Vagal Tone

► VasovagalVasovagal► PainPain► Occulocardiac reflexOcculocardiac reflex► Diving reflexDiving reflex► Carotid sinus massageCarotid sinus massage► Hypersensitive carotid sinus syndromeHypersensitive carotid sinus syndrome

Stimulation of carotid sinus leads to bradyasystole Stimulation of carotid sinus leads to bradyasystole and then to pre/syncopeand then to pre/syncope

Cardioinhibitory: >3s of asystole with carotid Cardioinhibitory: >3s of asystole with carotid stimulationstimulation

Vasodepressor effectsVasodepressor effects

Valvular DiseaseValvular Disease

►Due to extension of calcification into Due to extension of calcification into conduction systemconduction system

►Associated with AV and MV repair Associated with AV and MV repair ►Repair of VSD: including transcoronary Repair of VSD: including transcoronary

ablation of septal hypertrophy ablation of septal hypertrophy

InfectiousInfectious

►AVB with the following usually AVB with the following usually indicates poor prognosis:indicates poor prognosis:

►Myocarditis:Myocarditis: Viral: Cocksackie BViral: Cocksackie B Bacterial: DiptheriaBacterial: Diptheria Protozoal: Chagas diseaseProtozoal: Chagas disease Spirochetal: Lyme diseaseSpirochetal: Lyme disease Syphilis, toxoplasmosisSyphilis, toxoplasmosis

OtherOther► Congenital heart disease, neonatal SLE syndromeCongenital heart disease, neonatal SLE syndrome► Familial heart disease: cardiac sodium channel SCN5A linked Familial heart disease: cardiac sodium channel SCN5A linked

mutationsmutations► Cardiomyopathies: HOCM, amyloidosis, sarcoidosisCardiomyopathies: HOCM, amyloidosis, sarcoidosis► Endocrine causes:Endocrine causes:

HyperthyroidismHyperthyroidism hypoadrenalismhypoadrenalism HyperparathyroidismHyperparathyroidism AcromegalyAcromegaly

► Electrolyte abnormalities:Electrolyte abnormalities: Hyperkalemia: >6.3 meq/LHyperkalemia: >6.3 meq/L HypercalcemiaHypercalcemia HypermagnesemiaHypermagnesemia

► Infiltrative malignancies: lymphoma, multiple myelomasInfiltrative malignancies: lymphoma, multiple myelomas► Neuromuscular degenerative diseasesNeuromuscular degenerative diseases► Cardiac tumoursCardiac tumours

First Degree Heart BlockFirst Degree Heart Block

►SA node is normalSA node is normal Normal P waveNormal P wave

►AV node conducts more slowly than AV node conducts more slowly than normalnormal Prolonged PR interval >0.2sProlonged PR interval >0.2s PR interval is constantPR interval is constant

►Rest of conduction is normalRest of conduction is normal Normal QRSNormal QRS

First Degree AVBFirst Degree AVB

► Conduction delay can occur in: Conduction delay can occur in: ► Atrium: 3% of casesAtrium: 3% of cases

May be due to intratrial pathologyMay be due to intratrial pathology EKG findings: widening of P wave and decreased P wave EKG findings: widening of P wave and decreased P wave

voltage voltage ► AV node:AV node:

Most common siteMost common site Common causes: increased vagal tone, CCB, digoxin, BBCommon causes: increased vagal tone, CCB, digoxin, BB EKG findings: long PR interval with a narrow or wide P EKG findings: long PR interval with a narrow or wide P

wave and narrow QRSwave and narrow QRS► Bundle of His:Bundle of His:

Drugs that block sodium channels can impair Drugs that block sodium channels can impair depolarization and slow conduction (Quinidine, depolarization and slow conduction (Quinidine, procainamideprocainamide))

First Degree AVBFirst Degree AVB

►Clinical significance – noneClinical significance – none►Treatment – noneTreatment – none►May progress to 2May progress to 2ndnd or 3 or 3rdrd degree degree AVBAVB

Second Degree AVBSecond Degree AVB

►Some atrial impulses fail to reach the Some atrial impulses fail to reach the ventriclesventricles

►2 types:2 types: Mobitz Type I (Wenckebach): progressive Mobitz Type I (Wenckebach): progressive

PR interval lengthening to a non-PR interval lengthening to a non-conducted P waveconducted P wave

Mobitz Type II: PR interval constant prior Mobitz Type II: PR interval constant prior to P wave that does not conduct to the to P wave that does not conduct to the ventricles.ventricles.

SECOND DEGREE A-V BLOCK(MOBITZ I OR WENCKEBACH)

Mobitz Type I (Wenckebach) Mobitz Type I (Wenckebach) AVBAVB

► Most often involves AV nodeMost often involves AV node► Benign Benign ► Features:Features:

Gradually increasing PR intervalGradually increasing PR interval Gradually decreasing R-R intervalGradually decreasing R-R interval Dropped beatDropped beat Largest delay occurs in the first beat and then Largest delay occurs in the first beat and then

decreases beat to beat until block occurs and decreases beat to beat until block occurs and cycle is resetcycle is reset

Group beating: 3:2,4:3 etc.Group beating: 3:2,4:3 etc.

Second Degree Heart Block Second Degree Heart Block (2(2º)º)

Mobitz Type IMobitz Type I(Wenkebach)(Wenkebach)

PR PR PR DROPPED BEAT

Mobitz Type IMobitz Type I

►Clinical implications:Clinical implications: Often asymptomaticOften asymptomatic May have some symptoms eg lethargy, May have some symptoms eg lethargy,

confusionconfusion If cardiac output is reduced, patient may If cardiac output is reduced, patient may

experience angina, syncope or heart experience angina, syncope or heart failure due to bradycardia and resultant failure due to bradycardia and resultant hypoperfusion state.hypoperfusion state.

Can occur in athletes with high vagal toneCan occur in athletes with high vagal tone Elderly: aging prolongs cycle lengthElderly: aging prolongs cycle length

Further implications:Further implications:

► Underlying IHD:Underlying IHD: Mobitz type I can be complication of inferior MI as:Mobitz type I can be complication of inferior MI as: RCA supplies inferior and posterior walls and AV RCA supplies inferior and posterior walls and AV

and SA nodesand SA nodes Associated with increased mortalityAssociated with increased mortality

► Treatment:Treatment: Removing reversible causes (ischemia, increased Removing reversible causes (ischemia, increased

vagal tone, medicationsvagal tone, medications Pacemaker if symptomatic during dayPacemaker if symptomatic during day No pacemaker is symptoms at nightNo pacemaker is symptoms at night

► May progress to 3May progress to 3rdrd degree AVB degree AVB

MOBITZ TYPE II

Mobitz Type II AVBMobitz Type II AVB

► Always occurs below the AV nodeAlways occurs below the AV node 20% within Bundle of His20% within Bundle of His 80% in bundle branches 80% in bundle branches

► Widened QRS Widened QRS ► PR interval may be normal or slightly PR interval may be normal or slightly

prolonged but constantprolonged but constant► Non-conducted P wave on EKGNon-conducted P wave on EKG► Clinical implications:Clinical implications:

DizzinessDizziness PresyncopePresyncope SyncopeSyncope

Mobitz Type II AVBMobitz Type II AVB

►Type II is permanent and may progress Type II is permanent and may progress to higher levels of blockto higher levels of block

►Treatment:Treatment: Remove reversible causesRemove reversible causes Potential candidates for pacemaker Potential candidates for pacemaker

insertioninsertion

Second Degree AVB 2:1Second Degree AVB 2:1

►Unable to classify as Mobitz type I or IIUnable to classify as Mobitz type I or II►Ratio of 2 P waves to 1 QRSRatio of 2 P waves to 1 QRS►Clinical significance:Clinical significance:

Will be associated with symptoms Will be associated with symptoms (dizziness, lethargy etc.)(dizziness, lethargy etc.)

May progress to 3May progress to 3rdrd degree AVB degree AVB

►Treatment - pacemakerTreatment - pacemaker

THIRD DEGREE A-V BLOCK

Third degree (complete) AVBThird degree (complete) AVB

► No atrial impulses reach the ventricles due No atrial impulses reach the ventricles due failure of AV node therefore no P wave failure of AV node therefore no P wave conductionconduction

► AV dissociation (Ps marching through…)AV dissociation (Ps marching through…)► QRS complex:QRS complex:

Narrow: block at AV node to level of bundle of HisNarrow: block at AV node to level of bundle of His Wide: block below level of bundle of HisWide: block below level of bundle of His

► More distal the block the slower the escape More distal the block the slower the escape rhythmrhythm If <40bpm: pacemaker is unreliable causing If <40bpm: pacemaker is unreliable causing

profound bradycardia or asystoleprofound bradycardia or asystole Syncope is very commonSyncope is very common

Clinical SignificanceClinical Significance

► Clinical Implications:Clinical Implications: DizzinessDizziness PresyncopePresyncope SyncopeSyncope Ventricular tachycardiaVentricular tachycardia Ventricular fibrillationVentricular fibrillation ConfusionConfusion Can worsen angina and CHFCan worsen angina and CHF

► Treatment:Treatment: Pacemaker!Pacemaker!

Class I Indications for Class I Indications for Permanent Pacing in Adults per Permanent Pacing in Adults per

AHA/ACCAHA/ACC1.1. 33rdrd degree AVB at any anatomic level degree AVB at any anatomic level

associated with any of the following:associated with any of the following:• Symptomatic bradycardia (secondary to AVB)Symptomatic bradycardia (secondary to AVB)• Symptomatic bradycardia (secondary to drugs Symptomatic bradycardia (secondary to drugs

required for management of dysrhythmias or required for management of dysrhythmias or other medical conditions)other medical conditions)

• Documented asystole >3s or escape rate of Documented asystole >3s or escape rate of <40 bpm in awake, asymptomatic patient<40 bpm in awake, asymptomatic patient

• After ablation of AV nodeAfter ablation of AV node• Postoperative AVB that is not expected to Postoperative AVB that is not expected to

resolveresolve• Neuromuscular disease with AVB Neuromuscular disease with AVB

(neuromuscular dystrophies)(neuromuscular dystrophies)

2. Symptomatic bradycardia from 22. Symptomatic bradycardia from 2ndnd degree AVB degree AVB regardless of type or site of block.regardless of type or site of block.

3. Chronic bifascicular or trifascicular block with 3. Chronic bifascicular or trifascicular block with intermittent 3intermittent 3rdrd degree AV block or type II 2 degree AV block or type II 2ndnd degree degree AVB.AVB.

4. After AMI with any of the following:4. After AMI with any of the following: Persistent 2Persistent 2ndnd degree AVB at the His-Purkinje level degree AVB at the His-Purkinje level

with bilateral bundle branch block or 3with bilateral bundle branch block or 3rdrd degree AVB degree AVB at or below His-Purkinje systemat or below His-Purkinje system

Transient 2Transient 2ndnd or 3 or 3rdrd degree infranodal AVB and degree infranodal AVB and associated BBBassociated BBB

Symptomatic, persistent 2Symptomatic, persistent 2ndnd or 3 or 3rdrd degree AVB degree AVB5. Sinus node dysfunction with symptomatic bradycardia or 5. Sinus node dysfunction with symptomatic bradycardia or

chronotropic incompetence.chronotropic incompetence.6. Recurrent syncope caused by carotid sinus stimulation6. Recurrent syncope caused by carotid sinus stimulation ..

Pacemaker indications: Class IIaPacemaker indications: Class IIa

► Complete AVB without symptoms:Complete AVB without symptoms: >40bpm while awake = Class IIa indication>40bpm while awake = Class IIa indication UNLESS:UNLESS:

► Activity or exercise is limitedActivity or exercise is limited► Heart begins to enlargeHeart begins to enlarge► LV function is depressedLV function is depressed► LA enlargement is notedLA enlargement is noted► Intra- or infra-Hisian block issuspected with of without Intra- or infra-Hisian block issuspected with of without

QRS wideningQRS widening► QT interval prolongationQT interval prolongation► Ventricular arrhythmiasVentricular arrhythmias► Episodic profound bradycardia (during sleep or awake)Episodic profound bradycardia (during sleep or awake)

Pacemaker indications: take home Pacemaker indications: take home points!points!

►Complete AVB with:Complete AVB with: Associated symptomsAssociated symptoms Ventricular pauses >3sVentricular pauses >3s Resting HR <40 bpm while awake Resting HR <40 bpm while awake

= pacemaker!= pacemaker!

GrannyGranny

►Remember Granny?Remember Granny?►Well, she can be helped by some of Well, she can be helped by some of

the information in the next part of the the information in the next part of the talk…talk…

QuizQuiz

► Here is a photo of Here is a photo of the first pacemaker the first pacemaker invented (obviously invented (obviously not an internal not an internal device!)device!)

► Circa 1950Circa 1950► True or false: the True or false: the

inventor was inventor was Canadian…Canadian…

True!True!

► Courtesy of John Hopps - an engineer from Courtesy of John Hopps - an engineer from the University of Manitoba.the University of Manitoba.

► He recognized that if a heart stopped He recognized that if a heart stopped beating it could be started again by artificial beating it could be started again by artificial stimulation using mechanical or electric stimulation using mechanical or electric means.means.

► Current pacemakers provide electrical Current pacemakers provide electrical stimulation to cause cardiac contraction stimulation to cause cardiac contraction when intrinsic cardiac electrical activity is when intrinsic cardiac electrical activity is slow or absent.slow or absent.

A Brief History of PacemakersA Brief History of Pacemakers

Just kidding…but did you know?Just kidding…but did you know?► The implantable cardiac pacemaker was The implantable cardiac pacemaker was

discovered by mistake!discovered by mistake!► Wilson Greatbatch was building an oscillator Wilson Greatbatch was building an oscillator

to record heart sounds. When he to record heart sounds. When he accidentally installed a resistor with the accidentally installed a resistor with the wrong resistance into the unit, it began to wrong resistance into the unit, it began to give off a steady electrical pulse. Greatbatch give off a steady electrical pulse. Greatbatch realized that the small device could be used realized that the small device could be used to regulate the human heart. to regulate the human heart.

► After two years of refinements, he had hand-After two years of refinements, he had hand-crafted the world's first successful crafted the world's first successful implantable pacemaker (patent implantable pacemaker (patent #3,057,356). Until that time, the apparatus #3,057,356). Until that time, the apparatus used to regulate heartbeat was the size of a used to regulate heartbeat was the size of a television set, and painful to use. television set, and painful to use.

► Greatbatch later went one step further, Greatbatch later went one step further, inventing a corrosion-free lithium battery to inventing a corrosion-free lithium battery to power the pacemaker. All told, his power the pacemaker. All told, his pacemakers and batteries.pacemakers and batteries.

► Thus in 1985 the National Society of Thus in 1985 the National Society of Professional Engineers named Greatbatch's Professional Engineers named Greatbatch's invention one of the ten greatest invention one of the ten greatest engineering contributions to society of the engineering contributions to society of the last 50 years. last 50 years.

Pacemaker FunctionsPacemaker Functions

1.1. Stimulate cardiac depolarizationStimulate cardiac depolarization

2.2. Sense intrinsic cardiac functionSense intrinsic cardiac function

3.3. Respond to increased metabolic Respond to increased metabolic demand by providing rate responsive demand by providing rate responsive pacingpacing

4.4. Provide diagnostic information stored Provide diagnostic information stored by the pacemakerby the pacemaker

► Pulse generator: Pulse generator: power source or power source or batterybattery

► Leads or wiresLeads or wires► Cathode (negative Cathode (negative

electrode)electrode)► Anode (positive Anode (positive

electrode)electrode)► Apex of right Apex of right

ventricleventricle

IPG

Lead

Anode

Cathode

Pacemaker Components Combine Pacemaker Components Combine with Body Tissue to Form a with Body Tissue to Form a

Complete CircuitComplete Circuit

► Submuscular or Submuscular or subcutaneous subcutaneous implantation locationimplantation location

► Contains a lithium Contains a lithium battery that has a 4-battery that has a 4-10 year lifespan10 year lifespan

► Slow, gradual Slow, gradual decrease in power decrease in power over timeover time

► A sudden power A sudden power failure is very failure is very uncommonuncommon

Circuitry

Battery

The Pulse Generator:The Pulse Generator:

Electronic CircuitryElectronic Circuitry

►Sensing circuitSensing circuit►Timing circuitTiming circuit►Output circuitOutput circuit

Lead SystemLead System

BipolarBipolar► Lead has both Lead has both

negative, (Cathode) negative, (Cathode) distal and positive, distal and positive, (Anode) proximal (Anode) proximal electrodeselectrodes

► Separated by 1 cmSeparated by 1 cm► Larger diameter: Larger diameter:

more prone to more prone to fracturefracture

► Compatible with ICDCompatible with ICD

UnipolarUnipolar► Negative (Cathode) Negative (Cathode)

electrode in contact electrode in contact with heartwith heart

► Positive (Anode) Positive (Anode) electrode: metal electrode: metal casing of pulse casing of pulse generatorgenerator

► Prone to oversensingProne to oversensing► Not compatible with Not compatible with

ICDICD

Difference on an ECG? Difference on an ECG? Bipolar Bipolar

► current travels only current travels only a short distance a short distance between electrodes between electrodes

► small pacing spike: small pacing spike: <5mm<5mm

Anode

Cathode

+

-

Difference on an ECG? Difference on an ECG? Unipolar Unipolar

► current travels a current travels a longer distance longer distance between electrodes between electrodes

► larger pacing spike: larger pacing spike: >20mm>20mm

Anode

Cathode

+

-

Pacemaker CodePacemaker Code

IChamber

Paced

IIChamberSensed

IIIResponseto Sensing

IVProgrammableFunctions/Rate

Modulation

VAntitachy

Function(s)

V: Ventricle V: Ventricle T: Triggered P: Simple programmable

P: Pace

A: Atrium A: Atrium I: Inhibited M: Multi- programmable

S: Shock

D: Dual (A+V) D: Dual (A+V) D: Dual (T+I) C: Communicating D: Dual (P+S)

O: None O: None O: None R: Rate modulating O: None

S: Single (A or V)

S: Single (A or V)

O: None

Common PacemakersCommon Pacemakers

► VVIVVI Ventricular Pacing : Ventricular sensing; intrinsic QRS Ventricular Pacing : Ventricular sensing; intrinsic QRS

Inhibits pacer dischargeInhibits pacer discharge► VVIRVVIR

As above + has biosensor to provide Rate-As above + has biosensor to provide Rate-responsivenessresponsiveness

► DDDDDD Paces + Senses both atrium + ventricle, intrinsic Paces + Senses both atrium + ventricle, intrinsic

cardiac activity inhibits pacer d/c, no activity: trigger cardiac activity inhibits pacer d/c, no activity: trigger d/cd/c

► DDDRDDDR As above but adds rate responsiveness to allow for As above but adds rate responsiveness to allow for

exerciseexercise

Rate Responsive PacingRate Responsive Pacing

► When the need for oxygenated blood increases, When the need for oxygenated blood increases, the pacemaker ensures that the heart rate the pacemaker ensures that the heart rate increases to provide additional cardiac outputincreases to provide additional cardiac output

Adjusting Heart Rate to Activity

Normal Heart Rate

Rate Responsive PacingFixed-Rate Pacing

Daily Activities

Rate ResponseRate Response

► Rate responsive (also called rate modulated) Rate responsive (also called rate modulated) pacemakers provide patients with the ability pacemakers provide patients with the ability to vary heart rate when the sinus node to vary heart rate when the sinus node cannot provide the appropriate ratecannot provide the appropriate rate

► Rate responsive pacing is indicated for:Rate responsive pacing is indicated for: Patients who are chronotropically incompetent Patients who are chronotropically incompetent

(heart rate cannot reach appropriate levels during (heart rate cannot reach appropriate levels during exercise or to meet other metabolic demands)exercise or to meet other metabolic demands)

Patients in chronic atrial fibrillation with slow Patients in chronic atrial fibrillation with slow ventricular responseventricular response

Single ChamberSingle Chamber

► VVI - lead lies in VVI - lead lies in right ventricleright ventricle

► Independent of Independent of atrial activityatrial activity

► Use in AV Use in AV conduction diseaseconduction disease

Paced Rhythm RecognitionPaced Rhythm Recognition

AAI / 60

Paced Rhythm RecognitionPaced Rhythm Recognition

VVI / 60

DisadvantagesDisadvantagesAdvantagesAdvantages

Advantages and Disadvantages of Advantages and Disadvantages of Single-Chamber Pacing SystemsSingle-Chamber Pacing Systems

► Implantation of a Implantation of a single leadsingle lead

► Single ventricular Single ventricular lead does not provide lead does not provide AV synchronyAV synchrony

► Single atrial lead does Single atrial lead does not provide not provide ventricular backup if ventricular backup if A-to-V conduction is A-to-V conduction is lostlost

Dual ChamberDual Chamber

► Typically in pts with Typically in pts with nonfibrillating atria and nonfibrillating atria and intact AV conductionintact AV conduction

► Native P, paced P, Native P, paced P, native QRS, paced QRSnative QRS, paced QRS

► ECG may be ECG may be interpreted as interpreted as malfunction when none malfunction when none is presentis present

► May have fusion beatsMay have fusion beats

Rate = 60 bpm / 1000 msA-A = 1000 ms

APVP

APVP

V-AAV V-AAV

► Atrial Pace, Ventricular Pace (AP/VP)Atrial Pace, Ventricular Pace (AP/VP)

Four “Faces” of Dual Chamber Four “Faces” of Dual Chamber

PacingPacing

Rate = 60 ppm / 1000 msA-A = 1000 ms

AP VS

AP VS

V-AAV V-AAV

► Atrial Pace, Ventricular Sense (AP/VS)Atrial Pace, Ventricular Sense (AP/VS)

Four “Faces” of Dual Chamber Four “Faces” of Dual Chamber PacingPacing

ASVP

ASVP

Rate (sinus driven) = 70 bpm / 857 msA-A = 857 ms

► Atrial Sense, Ventricular Pace (AS/ VP)Atrial Sense, Ventricular Pace (AS/ VP)

V-AAV AV V-A

Four “Faces” of Dual Chamber Four “Faces” of Dual Chamber PacingPacing

Rate (sinus driven) = 70 bpm / 857 msSpontaneous conduction at 150 msA-A = 857 ms

ASVS

ASVS

V-AAV AV V-A

► Atrial Sense, Ventricular Sense (AS/VS)Atrial Sense, Ventricular Sense (AS/VS)

Four “Faces” of Dual Four “Faces” of Dual Chamber PacingChamber Pacing

Paced Rhythm RecognitionPaced Rhythm Recognition

DDD / 60 / 120

Paced Rhythm RecognitionPaced Rhythm Recognition

DDD / 60 / 120

Pacemaker InterventionsPacemaker Interventions►Magnet applicationMagnet application

No universal function of magnetNo universal function of magnet Does not inhibit or turn off pacemakerDoes not inhibit or turn off pacemaker Model-specific magnet that activate a reed Model-specific magnet that activate a reed

switch that coverts unit to asynchronous switch that coverts unit to asynchronous pacing at a pre-set rate that is no longer pacing at a pre-set rate that is no longer inhibited by patient’s intrinsic electrical inhibited by patient’s intrinsic electrical activity.activity.

► Interrogation / ProgrammingInterrogation / Programming Model-specific pacemaker programmer can Model-specific pacemaker programmer can

non-invasively obtain data on function and non-invasively obtain data on function and reset parametersreset parameters

Magnet ApplicationMagnet Application

Complications of Pacemaker Complications of Pacemaker ImplantationImplantation

►InfectionInfection►Venous obstructionVenous obstruction►Pacemaker SyndromePacemaker Syndrome

InfectionInfection

► 2% for wound and ‘pocket’ infection2% for wound and ‘pocket’ infection► 1% for bacteremia with sepsis1% for bacteremia with sepsis► NB pacemaker = foreign body!NB pacemaker = foreign body!► Patient may have symptoms of pain, local Patient may have symptoms of pain, local

inflammation, hematomainflammation, hematoma► Blood cultures should be drawnBlood cultures should be drawn► Culprits are Culprits are S. aureusS. aureus (60%) and (60%) and S. epidermidisS. epidermidis

(70%)(70%)► Vancomycin should be started pending culturesVancomycin should be started pending cultures► Pacemaker and leads are removed if bacteremicPacemaker and leads are removed if bacteremic► Temporised with transvenous pacingTemporised with transvenous pacing► iv antibiotics for 4-6 weeks with new components iv antibiotics for 4-6 weeks with new components

implanted.implanted.

Venous ObstructionVenous Obstruction

► Incidence 30-50%Incidence 30-50%► Can involve axillary, innominate, subclavian veins Can involve axillary, innominate, subclavian veins

and SVCand SVC► 1/3 have chronic complete venous obstruction 1/3 have chronic complete venous obstruction

but are asymptomatic due to collateralizationbut are asymptomatic due to collateralization► 0.5-3.5% develop symptoms which include: 0.5-3.5% develop symptoms which include:

edema, pain, venous engorgement of the edema, pain, venous engorgement of the ipsilateral arm to insertionipsilateral arm to insertion

► US, venography, CT to diagnose acute US, venography, CT to diagnose acute thrombosisthrombosis

► Heparin, lifetime warfarin; early thrombolytic Heparin, lifetime warfarin; early thrombolytic therapy is most effectivetherapy is most effective

Venous Access IssuesVenous Access Issues

► Pneumo / hemothoraxPneumo / hemothorax► Air embolismAir embolism► CONTROVERSIAL: association of PE with CONTROVERSIAL: association of PE with

pacemakerpacemaker► RARE: SVC syndrome from pacemaker lead-RARE: SVC syndrome from pacemaker lead-

induced thrombosisinduced thrombosis

Pacemaker SyndromePacemaker Syndrome

► 20% of patients present 20% of patients present with new complaints or with new complaints or worsening of initial worsening of initial symptoms that led to symptoms that led to pacemaker insertion pacemaker insertion

► More commonly with More commonly with singlesingle chamber pacerchamber pacer

► AV synchrony is lost AV synchrony is lost retrograde VA conduction retrograde VA conduction atrial contraction against atrial contraction against closed MV + TV closed MV + TV jugular jugular venous distention + atrial venous distention + atrial dilation dilation sx of CHF and sx of CHF and reflex vasodepressor effectsreflex vasodepressor effects

► Symptoms:Symptoms: Pre/syncopePre/syncope Orthostatic dizzinessOrthostatic dizziness FatigueFatigue Exercise intoleranceExercise intolerance WeaknessWeakness LethargyLethargy Chest fullness or painChest fullness or pain CoughCough Uncomfortable pulsations n Uncomfortable pulsations n

neck or abdomenneck or abdomen RUQ painRUQ pain OtherOther

Pacemaker SyndromePacemaker Syndrome

►1/3 of patients can adapt and these 1/3 of patients can adapt and these symptoms resolvesymptoms resolve

►1/3 require that a dual chamber pacer 1/3 require that a dual chamber pacer replace the single chamber pacerreplace the single chamber pacer

► If symptoms occur with dual chamber If symptoms occur with dual chamber pacer then optimizing timing of pacer then optimizing timing of ventricular pacing is keyventricular pacing is key

►BewareBeware: symptoms of pacemaker : symptoms of pacemaker syndrome and pacemaker malfunction syndrome and pacemaker malfunction are the same!are the same!

Pacemaker syndrome

bold indicates most common malfunctions

Pacemaker MalfunctionPacemaker Malfunction

Four categories:Four categories:• Failure to CaptureFailure to Capture• Inappropriate sensing: under or overInappropriate sensing: under or over• Inappropriate pacemaker rateInappropriate pacemaker rate

• The good news!The good news!• Rarely immediately life threateningRarely immediately life threatening• Occurs in <5% of patientsOccurs in <5% of patients

Failure to CaptureFailure to Capture

► Absence of pacemaker spikes despite Absence of pacemaker spikes despite indication to paceindication to pace

► Caused by:Caused by: Battery depletion - rareBattery depletion - rare Fracture of pacemaker lead – most common Fracture of pacemaker lead – most common

problemproblem Disconnection of lead from pulse generator unitDisconnection of lead from pulse generator unit Lead displacement – due to change cardiac Lead displacement – due to change cardiac Exit block – failure of an adequate stimulus to Exit block – failure of an adequate stimulus to

depolarize the paced chamber depolarize the paced chamber ► Seen in changes in endocardium in contact with pacing Seen in changes in endocardium in contact with pacing

system system i.e.i.e. infarction, ischemia, hyperkalemia, class III infarction, ischemia, hyperkalemia, class III antiarrhythmics (amiodarone, bertylium)antiarrhythmics (amiodarone, bertylium)

No CaptureNo Capture

►Pacemaker artifacts do not appear Pacemaker artifacts do not appear on the ECG; rate is less than the on the ECG; rate is less than the lower rate lower rate

Pacing output delivered; no evidence of pacing spike is seen

Failure to sense or capture in VVI

A: failure to capture atria in DDD

SensingSensing

►Sensing is the ability of the pacemaker Sensing is the ability of the pacemaker to “see” when a natural (intrinsic) to “see” when a natural (intrinsic) depolarization is occurringdepolarization is occurring Pacemakers sense cardiac depolarization Pacemakers sense cardiac depolarization

by measuring changes in electrical by measuring changes in electrical potential of myocardial cells between the potential of myocardial cells between the anode and cathodeanode and cathode

Accurate Sensing...Accurate Sensing...►Ensures that undersensing will not occur –Ensures that undersensing will not occur –

the pacemaker will not miss P or R waves the pacemaker will not miss P or R waves that should have been sensedthat should have been sensed

►Ensures that oversensing will not occur – Ensures that oversensing will not occur – the pacemaker will not mistake extra-the pacemaker will not mistake extra-cardiac activity for intrinsic cardiac eventscardiac activity for intrinsic cardiac events

►Provides for proper timing of the pacing Provides for proper timing of the pacing pulse – an appropriately sensed event pulse – an appropriately sensed event resets the timing sequence of the resets the timing sequence of the pacemakerpacemaker

Inappropriate sensing: Inappropriate sensing: UndersensingUndersensing

► Pacemaker incorrectly misses an intrinsic Pacemaker incorrectly misses an intrinsic depolarization depolarization paces despite intrinsic activity paces despite intrinsic activity

► Appearance of pacemaker spikes occurring Appearance of pacemaker spikes occurring earlierearlier than the programmed rate: “overpacing” than the programmed rate: “overpacing”

► May or may not be followed by paced complex: May or may not be followed by paced complex: depends on timing with respect to refractory depends on timing with respect to refractory periodperiod

► Causes:Causes: AMI, progressive fibrosis, lead displacement, AMI, progressive fibrosis, lead displacement,

fracture, poor contact with endocardiumfracture, poor contact with endocardium

Undersensing Undersensing

►Pacemaker does not “see” the intrinsic Pacemaker does not “see” the intrinsic beat, and therefore does not respond beat, and therefore does not respond appropriatelyappropriately

Intrinsic beat not sensed

Scheduled pace delivered

VVI / 60

UndersensingUndersensing

►An intrinsic depolarization that is An intrinsic depolarization that is present, yet not seen or sensed by present, yet not seen or sensed by the pacemakerthe pacemaker

P-wavenot sensed

Atrial UndersensingAtrial Undersensing

Inappropriate sensing: Inappropriate sensing: OversensingOversensing

►Detection of electrical activity not of Detection of electrical activity not of cardiac origin cardiac origin intermittent, intermittent, irregular pacing or inhibition of irregular pacing or inhibition of pacing activitypacing activity

►State of “underpacing”State of “underpacing”

Accurate Sensing Requires Accurate Sensing Requires That Extraneous Signals Be That Extraneous Signals Be

Filtered OutFiltered Out► Sensing amplifiers use filters that allow Sensing amplifiers use filters that allow

appropriate sensing of P waves and R appropriate sensing of P waves and R waves and reject inappropriate signalswaves and reject inappropriate signals

► Unwanted signals most commonly Unwanted signals most commonly sensed are:sensed are: T wavesT waves Far-field events (R waves sensed by the Far-field events (R waves sensed by the

atrial channel) atrial channel) Skeletal myopotentials (e.g., pectoral Skeletal myopotentials (e.g., pectoral

muscle myopotentials)muscle myopotentials)

OversensingOversensing

►An electrical signal other than the An electrical signal other than the intended P or R wave is detectedintended P or R wave is detected

Marker channel shows intrinsic

activity...

...though no activity is present

VVI / 60

Environmental Factors Environmental Factors Interfering with SensingInterfering with Sensing

► Electrocautery: causes temporary Electrocautery: causes temporary pacemaker inhibitionpacemaker inhibition

► MRI: alters pacemaker circuitry and results MRI: alters pacemaker circuitry and results in fixed-rate or asynchronous pacingin fixed-rate or asynchronous pacing

► Cellular phone: pacemaker inhibition, Cellular phone: pacemaker inhibition, asynchronous pacing asynchronous pacing

► Arc weldingArc welding► LithotripsyLithotripsy► MicrowavesMicrowaves► Mypotentials from muscleMypotentials from muscle

Inappropriate Pacemaker Inappropriate Pacemaker RateRate

► Rare reentrant tachycardia seen with dual Rare reentrant tachycardia seen with dual chamber pacers chamber pacers

► Premature atrial or ventricular contraction Premature atrial or ventricular contraction sensed by atrial lead sensed by atrial lead triggers ventricular triggers ventricular contraction contraction retrograde VA conduction retrograde VA conduction sensed by atrial lead sensed by atrial lead triggers ventricular triggers ventricular contraction contraction etc etc etc etc etc etc

► Tx: Magnet application: fixed rate, Tx: Magnet application: fixed rate, terminates tachyarrthymia,terminates tachyarrthymia,

► Reprogram to decrease atrial sensingReprogram to decrease atrial sensing

Causes of Pacemaker Causes of Pacemaker MalfunctionMalfunction

► Circuitry or power source of pulse Circuitry or power source of pulse generatorgenerator

► Pacemaker leadsPacemaker leads► Interface between pacing electrode Interface between pacing electrode

and myocardiumand myocardium► Environmental factors interfering Environmental factors interfering

with normal functionwith normal function

Pulse GeneratorPulse Generator

►Loose connectionsLoose connections Similar to lead fractureSimilar to lead fracture Intermittent failure to sense or paceIntermittent failure to sense or pace

►MigrationMigration Dissects along pectoral fascial planeDissects along pectoral fascial plane Failure to paceFailure to pace

►Twiddlers syndromeTwiddlers syndrome Manipulation Manipulation lead dislodgement lead dislodgement

LeadsLeads

►Dislodgement or fracture (anytime)Dislodgement or fracture (anytime) Incidence 2-3%Incidence 2-3% Occurs if pacemaker is placed mediallyOccurs if pacemaker is placed medially Failure to sense or paceFailure to sense or pace Dx with CXR, lead impedanceDx with CXR, lead impedance

► Insulation breaksInsulation breaks Current leaks Current leaks failure to capture failure to capture Dx with measuring lead impedance (low)Dx with measuring lead impedance (low)

Case continued…Case continued…

► Granny has had a pacemaker implanted 8d ago.Granny has had a pacemaker implanted 8d ago.► She went home feeling just fabulous!She went home feeling just fabulous!► She is in the ED with sharp, stabbing She is in the ED with sharp, stabbing

retrosternal chest pain that started after tea retrosternal chest pain that started after tea this morning. this morning.

► The pain is pleuritic.The pain is pleuritic.► When pressed, she says she was “quite winded” When pressed, she says she was “quite winded”

getting up the stairs from the cellar yesterday.getting up the stairs from the cellar yesterday.► Diagnosis?Diagnosis?

Cardiac PerforationCardiac Perforation

► Can happen early or late (days to weeks) post Can happen early or late (days to weeks) post implantationimplantation

► Need high index of suspicion because:Need high index of suspicion because: Often well tolerated due to small puncture sizeOften well tolerated due to small puncture size May auto-tamponadeMay auto-tamponade May be asymptomaticMay be asymptomatic May have hiccupsMay have hiccups

► May have pleuritic retrosternal chest pain, SOBMay have pleuritic retrosternal chest pain, SOB► May have increased pacing thresholdMay have increased pacing threshold► Px: may hear pericardial friction rubPx: may hear pericardial friction rub► CXR, FAST helpfulCXR, FAST helpful► Echo mandatory to rule outEcho mandatory to rule out

Pacemaker Mediated Pacemaker Mediated Tachycardia (PMT)Tachycardia (PMT)

► PMT is a paced rhythm, usually rapid, which is PMT is a paced rhythm, usually rapid, which is sustained by ventricular events conducted sustained by ventricular events conducted retrogradely (i.e., backwards) to the atria retrogradely (i.e., backwards) to the atria

► PMT can occur with loss of AV synchrony PMT can occur with loss of AV synchrony caused by:caused by:

PVCPVC

Atrial non-captureAtrial non-capture

Atrial undersensingAtrial undersensing

Atrial oversensingAtrial oversensing

Built in solution: PMT Built in solution: PMT InterventionIntervention

►Designed to interrupt a Pacemaker-Designed to interrupt a Pacemaker-Mediated TachycardiaMediated Tachycardia

DDD / 60 / 120

Pseudomalfunction: Pseudomalfunction: HysteresisHysteresis

►Allows a lower rate between sensed Allows a lower rate between sensed events to occur; paced rate is higherevents to occur; paced rate is higher

Lower Rate 70 ppm Hysteresis Rate 50 ppm

Management: HistoryManagement: History

►Most complications and malfunctions Most complications and malfunctions occur within first few weeks or monthsoccur within first few weeks or months

►Pacemaker identification card: should Pacemaker identification card: should tell you what you need to know about tell you what you need to know about the devicethe device

►Syncope, near syncope, orthostatic Syncope, near syncope, orthostatic dizziness, lightheaded, dyspnea, dizziness, lightheaded, dyspnea, palpitationspalpitations

►Pacemaker syndrome: diagnosis of Pacemaker syndrome: diagnosis of exclusionexclusion

Management: Physical ExamManagement: Physical Exam

►Look for :Look for : Fever: think pacemaker infectionFever: think pacemaker infection Cannon “a” waves: AV asynchronyCannon “a” waves: AV asynchrony Bibasilar crackles if CHFBibasilar crackles if CHF Pericardial friction rub if perforation of RVPericardial friction rub if perforation of RV

Management: adjunctsManagement: adjuncts

►CXR: CXR: Determine tip positionDetermine tip position Determine number of leads and positionDetermine number of leads and position

►EKGEKG May reveal failure to sense or paceMay reveal failure to sense or pace Low pacing rateLow pacing rate Abnormally rapid rhythm = pacemaker-Abnormally rapid rhythm = pacemaker-

mediated tachycardiamediated tachycardia

Management: ACLSManagement: ACLS

►Drugs and defibrillation as per ACLS Drugs and defibrillation as per ACLS guidelinesguidelines

►Recommended to keep paddles Recommended to keep paddles >10cm from pulse generator>10cm from pulse generator

►May transcutaneously paceMay transcutaneously pace►Transvenous pacing may be inhibited Transvenous pacing may be inhibited

by venous thrombosis: may need by venous thrombosis: may need fluoroscopic guidancefluoroscopic guidance

AMI + PacersAMI + Pacers

►Difficult diagnosisDifficult diagnosis►Most sensitive indicator is ST-T wave Most sensitive indicator is ST-T wave

changes on serial ECGchanges on serial ECG► If clinical presentation strongly suggestive If clinical presentation strongly suggestive

then should treat as AMIthen should treat as AMI►Coarse VF may inhibit pacer (oversensing)Coarse VF may inhibit pacer (oversensing)►Successful resuscitation may lead to Successful resuscitation may lead to

failure to capture (catecholamines, failure to capture (catecholamines, ischemia)ischemia)

DispositionDisposition► AdmitAdmit

Pacemaker infections /unexplained fever or Pacemaker infections /unexplained fever or WBCWBC

Myocardial perforationMyocardial perforation Lead # or dislodgementLead # or dislodgement Wound dehiscence / extrusion or erosionWound dehiscence / extrusion or erosion Failure to pace, sense, or captureFailure to pace, sense, or capture Ipsilateral venous thrombosisIpsilateral venous thrombosis Unexplained syncopeUnexplained syncope Twiddlers syndromeTwiddlers syndrome

DispositionDisposition

►Potentially fixable in ED w/ helpPotentially fixable in ED w/ help Pacemaker syndromePacemaker syndrome Pacemaker-mediated tachycardiaPacemaker-mediated tachycardia OversensingOversensing Diaphragmatic pacingDiaphragmatic pacing Myopotential inhibitorsMyopotential inhibitors

Temporary Pacing ModalitiesTemporary Pacing Modalities

1.1. Transcutaneous Transcutaneous

2.2. TransvenousTransvenous

Emergency PacingEmergency Pacing

►Hemodynamically compromising Hemodynamically compromising bradycardiabradycardia

►Bradycardia with escape rhythmsBradycardia with escape rhythms►Overdrive pacing of refractory Overdrive pacing of refractory

tachycardiatachycardia►Bradyasystolic cardiac arrest (within 5 Bradyasystolic cardiac arrest (within 5

minutes)minutes)►Bradycardia dependent ventricular Bradycardia dependent ventricular

tachyarrhythmia (Torsade-de-Pointes)tachyarrhythmia (Torsade-de-Pointes)

Indications for temporary Indications for temporary pacingpacing

► With AMI with:With AMI with: Symptomatic sinus node dysfunctionSymptomatic sinus node dysfunction Mobitz type II 2Mobitz type II 2ndnd degree AVB degree AVB 33rdrd degree AVB degree AVB New left, right or alternating BBB or bi-fascicular New left, right or alternating BBB or bi-fascicular

blockblock Before electrical cardioversion of a patient with Before electrical cardioversion of a patient with

sick sinus syndrome or with a high level of sick sinus syndrome or with a high level of dependency to a permanent pacemakerdependency to a permanent pacemaker

Prior to permanent pacemaker implantationPrior to permanent pacemaker implantation Prior to PA cath insertion if underlying LBBB Prior to PA cath insertion if underlying LBBB

Transcutaneous Pacing Transcutaneous Pacing Pitfalls:Pitfalls:

► Capture is obtained between 40-80 mA Capture is obtained between 40-80 mA regardless of age, body weight and BSAregardless of age, body weight and BSA

► May see INCREASED pacing threshold with:May see INCREASED pacing threshold with: Suboptimal lead positionSuboptimal lead position Poor skin-electrode contactPoor skin-electrode contact Post surgical chestwall disruptionPost surgical chestwall disruption EmphysemaEmphysema Pericardial effusionPericardial effusion PPVPPV Hypoxia/ischemia/shock/acidosis/hyperkalemiaHypoxia/ischemia/shock/acidosis/hyperkalemia After electrical cardioversion/defibrillationAfter electrical cardioversion/defibrillation After prolonged resuscitation/arrestAfter prolonged resuscitation/arrest

Transcutaneous PacingTranscutaneous Pacing

► Initiation of pacing:Initiation of pacing: Use maximal current output and asynch Use maximal current output and asynch

settingsetting Adjust current to ~10mA above thresholdAdjust current to ~10mA above threshold Confirm capture by:Confirm capture by:

►Pulse palpationPulse palpation►DopplerDoppler►Arterial line tracingArterial line tracing

Pitfalls/ComplicationsPitfalls/Complications

►Failure to recognise underlying VFFailure to recognise underlying VF►Failure to recognise that pacemaker is Failure to recognise that pacemaker is

NOTNOT capturing capturing►Complications:Complications:

PainfulPainful Induction of arrhythmiasInduction of arrhythmias Tissue damageTissue damage

Transvenous PacingTransvenous Pacing

►Most consistent and reliable means of Most consistent and reliable means of temporary pacingtemporary pacing

►Can permit atrial and/or ventricular Can permit atrial and/or ventricular pacingpacing

►StableStable►Well toleratedWell tolerated►Significant potential complicationsSignificant potential complications

Transvenous PacingTransvenous Pacing

► 4 letter coding system:4 letter coding system: 11stst letter: indicates letter: indicates pacedpaced chamber (V,A,D) chamber (V,A,D) 22ndnd letter: indicates letter: indicates sensedsensed chamber (V,A,D) chamber (V,A,D) 33rdrd letter: letter: mode of responsemode of response when an event is when an event is

sensed sensed ► I = inhibitedI = inhibited► T = triggeredT = triggered► D = inhibited or triggeredD = inhibited or triggered► 0 = neither inhibited, nor triggered0 = neither inhibited, nor triggered

44thth letter: R indicates letter: R indicates rate responsivenessrate responsiveness (only in (only in permanent device)permanent device)

Can be uni or bipolarCan be uni or bipolar

► Unipolar SystemUnipolar System► SimpleSimple► Less sophisticated Less sophisticated

electrodeelectrode► Dipole is between tip of Dipole is between tip of

electrode and electrode and generatorgenerator

► Higher risk of Higher risk of oversensingoversensing

► Larger spike on EKGLarger spike on EKG

► Bipolar SystemBipolar System► More complex More complex

electrodeelectrode► Larger electrodeLarger electrode► Dipole is at tip of Dipole is at tip of

electrodeelectrode► Lower risk of Lower risk of

oversensingoversensing► Small spike on EKGSmall spike on EKG► Higher risk of electrode Higher risk of electrode

failurefailure

Contraindications to Contraindications to transvenous pacingtransvenous pacing

►Tricuspid valve mechanical prosthesisTricuspid valve mechanical prosthesis►Existing endocarditisExisting endocarditis► Infected endocardial pacemaker leadInfected endocardial pacemaker lead►Sepsis/bacteremiaSepsis/bacteremia►Ventricular arrhythmiasVentricular arrhythmias

CaptureCapture

► Depends on:Depends on: Stable catheter positionStable catheter position Viability of paced myocardial tissueViability of paced myocardial tissue Electrical integrity of pacing systemElectrical integrity of pacing system

► Most common cause of lost capture is lead Most common cause of lost capture is lead dislodgement/perforationdislodgement/perforation

► Other causes include:Other causes include: Poor endocardial contactPoor endocardial contact Local myocardial necrosis/fibrosis/inflammation/ edemaLocal myocardial necrosis/fibrosis/inflammation/ edema Hypoxia/acidosis/electrolyte abnormalities/drug effectsHypoxia/acidosis/electrolyte abnormalities/drug effects Lead fractureLead fracture Generator malfunction/battery failureGenerator malfunction/battery failure Unstable electrical connectionsUnstable electrical connections

Sensing problemsSensing problems

► UndersensingUndersensing► Lead dislodgement/ Lead dislodgement/

perforationperforation► Local tissue Local tissue

necrosis/fibrosisnecrosis/fibrosis► Lead fractureLead fracture► ElectrocauteryElectrocautery► Generator malfunctionGenerator malfunction► Unstable electrical Unstable electrical

connectionsconnections

► OversensingOversensing► P wave sensingP wave sensing► T wave sensingT wave sensing► Myopotential sensingMyopotential sensing► Electromagnetic Electromagnetic

interferenceinterference► Poor electrical Poor electrical

contacts, contacts, connectionsconnections

► Lead fractureLead fracture

ComplicationsComplications

► ArrhythmiasArrhythmias► Thromboembolic events - ? Need to Thromboembolic events - ? Need to

anticoagulateanticoagulate► Clinical infection/phlebitisClinical infection/phlebitis► BacteremiaBacteremia► PerforationPerforation► Knotting of catheterKnotting of catheter► Tricuspid valve damageTricuspid valve damage► Induction of RBBBInduction of RBBB► Phrenic nerve or diaphragmatic pacing Phrenic nerve or diaphragmatic pacing

without myocardial perforationwithout myocardial perforation

Myocardial PerforationMyocardial Perforation

► SymptomsSymptoms► Pericardial chest painPericardial chest pain► Shoulder painShoulder pain► Diaphragmatic Diaphragmatic

pacingpacing► Skeletal muscle Skeletal muscle

pacingpacing► DyspneaDyspnea► Hypotension (?Hypotension (?

tamponade)tamponade)

► SignsSigns► Pericardial rubPericardial rub► Intercostal or Intercostal or

diaphragmatic diaphragmatic pacingpacing

► Failure to pace or Failure to pace or sensesense

► New pericardial New pericardial effusion or effusion or tamponadetamponade

InvestigationsInvestigations

►EKG:EKG: Change in QRS morphology +/- axisChange in QRS morphology +/- axis Failure to pace or senseFailure to pace or sense Pericarditis patternPericarditis pattern

►CXR:CXR: Change in lead positionChange in lead position Extra-cardiac location of lead tipExtra-cardiac location of lead tip

Thanks!Thanks!

ReferencesReferences► Thanks to Karen Hillier, Pacemaker Nurse Clinician Thanks to Karen Hillier, Pacemaker Nurse Clinician ► Rosens: Chapter 28Rosens: Chapter 28► Barold, S. Serge. Cardiac pacemakers step by step : an illustrated Barold, S. Serge. Cardiac pacemakers step by step : an illustrated

guide. Blackwell, 2004. guide. Blackwell, 2004. ► Haim M et al. Frequency and prognostic significance of high degree Haim M et al. Frequency and prognostic significance of high degree

atrioventricular block in patients with first non-Q wave acute atrioventricular block in patients with first non-Q wave acute myocardial infarction. Am J Cardiol. 1997;79:674.myocardial infarction. Am J Cardiol. 1997;79:674.

► Lamas G et al. Ventricular Pacing or Dual Chamber Pacing for Sinus Lamas G et al. Ventricular Pacing or Dual Chamber Pacing for Sinus Node Dysfunction. NEJM. 2002;346(24):1854-61.Node Dysfunction. NEJM. 2002;346(24):1854-61.

► Lamas G et al. A simplified approach to predicting the occurrence of Lamas G et al. A simplified approach to predicting the occurrence of complete heart block during acute myocardial infarction. Am J Cardiol. complete heart block during acute myocardial infarction. Am J Cardiol. 1986;57:1213.1986;57:1213.

► Mangrum JM, DiMarco JP. The evaluation and Management of Mangrum JM, DiMarco JP. The evaluation and Management of bradycardia. NEJM. 2000;342(10):703-9.bradycardia. NEJM. 2000;342(10):703-9.

► www.uptodate.comwww.uptodate.com for heart blocks and pacemaker information for heart blocks and pacemaker information► ACC/AHA Guidelines for Pacemaker implantation: ACC/AHA Guidelines for Pacemaker implantation:

http://www.acc.org/qualityandscience/clinical/guidelines/april98/jac550http://www.acc.org/qualityandscience/clinical/guidelines/april98/jac5507gtc.htm7gtc.htm

CHB and AMICHB and AMI

► Incidence of new CHB 5.4%Incidence of new CHB 5.4%►Occurring 2.6 days post MIOccurring 2.6 days post MI►Developed in:Developed in:

>60 y.o.>60 y.o. Comorbid CHFComorbid CHF Associated with increased risk of Associated with increased risk of

developing cardiogenic shockdeveloping cardiogenic shock

MILIS Trial: Predictors of CHBMILIS Trial: Predictors of CHB

► 1 point for each of the following:1 point for each of the following: PR prolongationPR prolongation 22ndnd degree AVB degree AVB LAFB or LPFBLAFB or LPFB LBBBLBBB RBBBRBBB

► Risk of Progression:Risk of Progression: 1.2-6.8% with score of zero1.2-6.8% with score of zero 7.8-10% with score of 17.8-10% with score of 1 25-30% with score of 225-30% with score of 2 36% with a score of 3 or more36% with a score of 3 or more

CHB and NSTEMICHB and NSTEMI

►SPRINT Study Group:SPRINT Study Group: 610 patients with first NSTEMI:610 patients with first NSTEMI:

►22ndnd or 3 or 3rdrd degree AVB in 7% (45/610) degree AVB in 7% (45/610)►These patients had:These patients had:

Increased rate of cardiac arrestIncreased rate of cardiac arrest Increased rate of CHFIncreased rate of CHF Increased rate of elevated cardiac markersIncreased rate of elevated cardiac markers Higher in hospital mortalityHigher in hospital mortality Larger and more complicated infarctionsLarger and more complicated infarctions No difference in mortality outcomes at 5 years No difference in mortality outcomes at 5 years

CHB post AMI and the ElderlyCHB post AMI and the Elderly

► Incidence 4.7%Incidence 4.7%►New AVB in 3.2%New AVB in 3.2%►More commonly associated with More commonly associated with

inferior MI compared to anterior MI inferior MI compared to anterior MI (7.3 vs 3.0%)(7.3 vs 3.0%)

►Associated with increased in hospital Associated with increased in hospital mortality but no change in long term mortality but no change in long term mortality outcomesmortality outcomes

Infarct location and conduction Infarct location and conduction disturbancesdisturbances

► Inferior MIs:Inferior MIs: Conduction changes can occur acutely to days post MIConduction changes can occur acutely to days post MI RCA supplies the SA node, AV node, and bundle of His RCA supplies the SA node, AV node, and bundle of His 1.1. Sinus bradycardiaSinus bradycardia

Up to 40% of patients within hours of infarctUp to 40% of patients within hours of infarct Due to increased vagal toneDue to increased vagal tone May be due to transient sinus node dysfunctionMay be due to transient sinus node dysfunction

2.2. Mobitz type I AVBMobitz type I AVB 9.8% of patients9.8% of patients May be transient (x days)May be transient (x days)

3.3. CHBCHB From an infranodal lesionFrom an infranodal lesion Narrow QRSNarrow QRS Develops from 1Develops from 1stst to 3 to 3rdrd degree AVB degree AVB Asymptomatic bradycardiaAsymptomatic bradycardia Resolves within 5-7dResolves within 5-7d

►Anterior MI:Anterior MI: 1st degree AVB below AV node with 1st degree AVB below AV node with

widened QRSwidened QRS 22ndnd degree type II with unpredictable degree type II with unpredictable

clinical course with block progressionclinical course with block progression CHB occurs in first 24h:CHB occurs in first 24h:

►Abrupt onsetAbrupt onset►Wide and unstable escape ryhthmWide and unstable escape ryhthm►High mortality: arrhythmias and pump failureHigh mortality: arrhythmias and pump failure►Due to extensive necrosis of bundle branchesDue to extensive necrosis of bundle branches

Permanent PacingPermanent Pacing

►33rdrd degree AVB within or below the His- degree AVB within or below the His-Purkinje systemPurkinje system

►Persistent 2Persistent 2ndnd degree AVB degree AVB►Transient advanced infranodal AVB Transient advanced infranodal AVB

with bundle branch blocks due too with bundle branch blocks due too infarctioninfarction

►Symptomatic and persistent 2Symptomatic and persistent 2ndnd or 3 or 3rdrd degree AVB degree AVB

ACC/AHA/NASPE: indications for permanent pacing in acquired ACC/AHA/NASPE: indications for permanent pacing in acquired atrioventricular (AV) block in adultsatrioventricular (AV) block in adults

► Class IClass I► 1. Third-degree and advanced second-degree AV block at any 1. Third-degree and advanced second-degree AV block at any

anatomic level, associated with any one of the following conditions: anatomic level, associated with any one of the following conditions: a. Bradycardia with symptoms (including heart failure) presumed to be a. Bradycardia with symptoms (including heart failure) presumed to be

due to AV block. (Level of Evidence: C)due to AV block. (Level of Evidence: C) b. Arrhythmias and other medical conditions that require drugs that b. Arrhythmias and other medical conditions that require drugs that

result in symptomatic bradycardia. (Level of Evidence: C)result in symptomatic bradycardia. (Level of Evidence: C) c. Documented periods of asystole 3.0 seconds or any escape rate <40 c. Documented periods of asystole 3.0 seconds or any escape rate <40

beats per minute in (bpm) in awake, symptom-free patients. (Levels of beats per minute in (bpm) in awake, symptom-free patients. (Levels of Evidence: B, C)Evidence: B, C)

d. After catheter ablation of the AV junction. (Levels of Evidence: B, C) d. After catheter ablation of the AV junction. (Levels of Evidence: B, C) There are no trials to assess outcome without pacing, and pacing is There are no trials to assess outcome without pacing, and pacing is virtually always planned in this situation unless the operative procedure virtually always planned in this situation unless the operative procedure is AV junction modification. is AV junction modification.

e. Postoperative AV block that is not expected to resolve after cardiac e. Postoperative AV block that is not expected to resolve after cardiac surgery. (Level of Evidence: C)surgery. (Level of Evidence: C)

f. Neuromuscular diseases with AV block, such as myotonic muscular f. Neuromuscular diseases with AV block, such as myotonic muscular dystrophy, Kearns-Sayre syndrome, Erbs dystrophy (limb-girdle), and dystrophy, Kearns-Sayre syndrome, Erbs dystrophy (limb-girdle), and peroneal muscular atrophy, with or without symptoms, because there peroneal muscular atrophy, with or without symptoms, because there may be unpredicatable progression of AV conduction disease. (Level of may be unpredicatable progression of AV conduction disease. (Level of Evidence B:)Evidence B:)

► 2. Second-degree AV block regardless of type or site of block, with 2. Second-degree AV block regardless of type or site of block, with associated symptomatic bradycardia. (Level of Evidence: B)associated symptomatic bradycardia. (Level of Evidence: B)

Class IIaClass IIa 1. Asymptomatic third-degree AV block at any anatomic 1. Asymptomatic third-degree AV block at any anatomic

site with average awake ventricular rates of 40 beats per site with average awake ventricular rates of 40 beats per minute or faster especially if cardiomegaly or left minute or faster especially if cardiomegaly or left ventricular (LV) dysfunction is present. (Levels of Evidence: ventricular (LV) dysfunction is present. (Levels of Evidence: B, C)B, C)

2. Asymptomatic type II second-degree AV block with a 2. Asymptomatic type II second-degree AV block with a narrow QRS. When type II second-degree AV block occurs narrow QRS. When type II second-degree AV block occurs with a wide QRS, pacing becomes a Class I with a wide QRS, pacing becomes a Class I recommendation. (Level of Evidence: B)recommendation. (Level of Evidence: B)

3. Asymptomatic type I second-degree AV block at intra- or 3. Asymptomatic type I second-degree AV block at intra- or infra-His levels found at electrophysiological study infra-His levels found at electrophysiological study performed for other indications. (Level of Evidence: B)performed for other indications. (Level of Evidence: B)

4. First- or second-degree AV block with symptoms 4. First- or second-degree AV block with symptoms suggestive of pacemaker syndrome. (Level of Evidence: B)suggestive of pacemaker syndrome. (Level of Evidence: B)

► Adapted from Gregoratos, G, Abrams, J, Epstein, AE, Adapted from Gregoratos, G, Abrams, J, Epstein, AE, et al. Circulation 2002; 106:2145. et al. Circulation 2002; 106:2145.